I have just began making cc myself. And now I want to make decals. I use gimp and sims 4 studios for my makings. I figured out the basics, but the decal i used to make my own still shows slightly thro...
There are other textures you need to take care of (don't delete). Try making them blank and see if it helps. http://sims4studio.com/thread/1079/get-eas-bump-specular-maps